Most of the collagen in oral soft connective tissues resists extraction by salt and acetic acid and is, thus, "insoluble". Previous data obtained in our laboratory suggests that the maturation of collagen (operationally defined as insolubilization) is rapid in oral tissues. Further, this maturation process is relatively insensitive to inhibition by beta-aminopropionitrile, a known inhibitor of aldimine-type cross-linking. Our research efforts will be directed towards characterizing the nature of this insoluble collagen and the mechanism responsible for its insolubilization. BIBLIOGRAPHIC REFERENCES: M. Schneir, I. Vogan, H. Yu, J. Yavelow, A. Liu-Montcalm and D. Furuto. Ability of Salt and Acetic Acid to Extract Human and Animal Gingival Collagen. J. Dent. Res. 54: 1095 (1975). Donald Furuto and Michael Schneir. Concomitant Tissue Accumulation of "Collagen-Associated" Sialoglycoproteins and Salt-Insoluble Collagen During Rat Skin Maturation. Mechanism of Ageing and Develop. 4, 97-101 (1975).